This recipe shows you how to set up your PostgreSQL system so that it requires clients to present a valid X.509 certificate before allowing them to connect.
This can be used as an additional security layer to use double authentication, where the client must both have a valid certificate to set up the SSL connection and also know the database user's password. It can also be used as the sole authentication method, where the PostgreSQL server will first verify the client connection using the certificate presented by the client, and then retrieve the username from the same certificate.
